title: Dark formation of hydroxyl radical in Arctic soil and surface waters.
abstract: Hydroxyl radical (•OH) is a highly reactive and unselective oxidant in atmospheric and aquatic systems. Current understanding limits the role of DOM-produced •OH as an oxidant in carbon cycling mainly to sunlit environments where •OH is produced photochemically, but a recent laboratory study proposed a sunlight-independent pathway in which •OH forms during oxidation of reduced aquatic dissolved organic matter (DOM) and iron. Here we demonstrate this non-photochemical pathway for •OH formation in natural aquatic environments. Across a gradient from dry upland to wet lowland habitats, •OH formation rates increase with increasing concentrations of DOM and reduced iron, with highest •OH formation predicted at oxic-anoxic boundaries in soil and surface waters. Comparison of measured vs expected electron release from reduced moieties suggests that both DOM and iron contribute to •OH formation. At landscape scales, abiotic DOM oxidation by this dark •OH pathway may be as important to carbon cycling as bacterial oxidation of DOM in arctic surface waters.
authors.affiliation: Institute of Biogeochemistry and Pollutant Dynamics, Swiss Federal Institute of Technology (ETH) , Zurich, Switzerland.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Page
authors.forename: George W
authors.initials: GW
authors.lastname: Kling
authors.forename: Michael
authors.initials: M
authors.lastname: Sander
authors.forename: Katherine H
authors.initials: KH
authors.lastname: Harrold
authors.forename: J Robert
authors.initials: JR
authors.lastname: Logan
authors.forename: Kristopher
authors.initials: K
authors.lastname: McNeill
authors.forename: Rose M
authors.initials: RM
authors.lastname: Cory
mesh_terms: D001110:Arctic Regions; D002244:Carbon / Q000032:analysis; D003624:Darkness; D017753:Ecosystem; D004583:Electrons; D004777:Environment; D017665:Hydroxyl Radical / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D009930:Organic Chemicals / Q000032:analysis; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis; D012987:Soil / Q000737:chemistry*; D012995:Solubility; D014867:Water / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D012987:Soil; D014867:Water; D017665:Hydroxyl Radical; D002244:Carbon; D007501:Iron; D010100:Oxygen